Excessive speed leads to tugboat accidents

On 7 August 2022, CC Portland grounded outside the Corpus Christi Ship Channel while attempting to secure a towline on the bow of inbound LNG Fukurokuju.

Both vessels were sailing at higher speeds than necessary for safe harbour-assist manoeuvres, resulting in US$1.3M in damage to the 31-m, 293-gt tugboat and 23 litres of oil pollution.

In reaction to both accidents, the NTSB encourages owners and operators of azimuth stern drive (ASD) tugboats to set speed limits for bow-to-bow harbour-assist operations. 

“The risk of a casualty during these operations with ASD tugboats increases with higher speed,” NTSB investigators says in the final report. “Higher speed reduces the amount of reserve propulsion power available to the operator. If the tugboat moves out of position, the operator has less power to regain position as compared to the same manoeuvre at a lower ship transit speed.”

Contributing to the grounding was the lack of a company policy regarding maximum allowable speed for bow-assist manoeuvres. 

These limits may vary for different classes of tugboats based on design. “Tugboat operators should communicate these predetermined speed limits to pilots and ship masters in command of the vessels they are assisting before engaging in these manoeuvres,” the NTSB says.

CC Portland has a beam of 13 m, a draught of 6 m, ABS class and around 3,340 kW of power, derived from two Caterpillar 3516E diesel engines, rated 1,670 kW each.

The NTSB also investigated a fire on towing vessel Mary Dupre in June 2022, which was deemed a total constructive loss estimated at US$1M.

Fire broke out in a stateroom on board while Mary Dupre was pushing a barge of bio-diesel fuel (pyrolysis fuel oil) on the Gulf Intracoastal Waterway near Freeport, Texas.

After the incident, other towing vessels retrieved the barge from Mary Dupre, extinguished the fire, and evacuated the four crew members. 

NTSB investigators determined the probable cause of the fire as undetected cracks in the starboard muffler that allowed exhaust gases from an operating engine to escape and ignite wooden structures affixed to the common bulkhead of an accommodation space. 

Contributing to the extent of the fire damage was the substantial use of combustible materials in the joinery, outfitting and furnishings in the accommodation spaces.​

In conclusion, the NTSB urged tug owners to inspect exhaust components using handheld equipment – such as inspection mirrors, video equipment or thermal imaging equipment – to detect deficiencies.  

“Exhaust systems generate heat and often run through tight spaces that are difficult to access and inspect and are often located near materials or equipment that obstruct entry and direct observation,” says the NTSB. “It is good practice to include these areas in periodic fire safety inspections.” 

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